Quoting Florian Fainelli <f.faine...@gmail.com>:
On 1/23/19 1:20 PM, René van Dorst wrote:
Without this patch sfp code retries to read the full struct sfp_eeprom_id
id out of the SFP eeprom. Sizeof(id) is 96 bytes.
My i2c hardware, Mediatek mt7621, has a rx buffer of 64 bytes.
So sfp_read gets -NOSUPPORTED back on his turn return -EAGAIN.
Same issue is with the SFP_EXT_STATUS data which is 92 bytes.
By split-up the request in multiple smaller requests with a max size of i2c
max_read_len, we can readout the SFP module successfully.
Tested with MT7621 and two Fiberstore modules SFP-GB-GE-T and SFP-GE-BX.
Signed-off-by: René van Dorst <opensou...@vdorst.com>
---
drivers/net/phy/sfp.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)
diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index fd8bb998ae52..1352a19571cd 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -367,7 +367,28 @@ static void sfp_set_state(struct sfp *sfp,
unsigned int state)
static int sfp_read(struct sfp *sfp, bool a2, u8 addr, void *buf,
size_t len)
{
- return sfp->read(sfp, a2, addr, buf, len);
+ const struct i2c_adapter_quirks *q = sfp->i2c->quirks;
+ int ret;
+ size_t rx_bytes = 0;
+
+ /* Many i2c hw have limited rx buffers, split-up request when needed. */
+ while ((q->max_read_len) && (len > q->max_read_len)) {
+ ret = sfp->read(sfp, a2, addr, buf, q->max_read_len);
+ if (ret < 0)
+ return ret;
+ rx_bytes += ret;
+ addr += q->max_read_len;
+ buf += q->max_read_len;
+ len -= q->max_read_len;
+ }
sfp->read defaults to sfp_i2c_read() but it is possible to override that
by registering a custom sfp_bus instance (nothing does it today, but
that could obviously change), so there is no guarantee that
sfp->i2c->quirks is applicable unless sfp_i2c_read() is used.
sfp_i2c_read() is presumably where the max_read_len splitting should
occur, or better yet, should not i2c_transfer() take care of that on its
own? That way there would be no layering violation of having to fetch
the quirk bitmask for the i2c adapter being used, that is something that
should belong in the core i2c framework.
Yes it is better to put it in sfp_i2c_read().
I think it is best to handle the split-up within the driver.
The driver knows how to talk to the device and may apply device quirks.
Also tda1004x [0] and TPM [1] driver also handles it within the driver itself.
TPM driver just try to send the want size and split-up request to
I2C_SMBUS_BLOCK_MAX when a -EOPNOTSUPP returns, just retries it a number of
times.
I can do the same but I have to pick a minimum size.
Looking in SSF-8472rev12.2.1 they don't limit the way you access the device.
So use I2C_SMBUS_BLOCK_MAX of 32 bytes is sufficient or lookup the i2c
quirk max_read_len is also an option.
Grepping thru the i2c busses I see only 2 devices which has less then 32 bytes
of buffer. i2c-nvidia-gpu (Nvidia GPU) and i2c-pmcmsp (microcontroller
MSP71xx).
Both are unlikely to be used for these kind of applications.
I think I2C_SMBUS_BLOCK_MAX is safe to use.
Greats,
René
[0]
https://elixir.bootlin.com/linux/v5.0-rc3/source/drivers/media/dvb-frontends/tda1004x.c#L319
[1]
https://elixir.bootlin.com/linux/v5.0-rc3/source/drivers/char/tpm/tpm_i2c_infineon.c#L158
